The Null Personality
No personality? How is that possible? What can be called the "null personality" (or "social cipher") may be interpreted as utterly unresponsive to others or otherwise "mechanical", robotic, inhibited, disengaged and muted in interactions with them, much as patients in clinical catatonic states or individuals who are otherwise psychologically and socially extremely withdrawn are.
However rare or theoretical, the null personality does serve as a reference point for some imaginable scale of d egrees of personality. Farther along the developed personality spectrum lie the very shy and socially awkward, who may come across as navigating socially with the emergency brake on. Almost as unappealing - the apathetic and otherwise detached.